Multicenter, retrospective-prospective, real-world observational study, with the aim of evaluating tolerability and efficacy in a population of patients treated according to clinical practice outside of studies randomized.

Patients affected by will be included in the study and analyzed HER2 positive breast cancer with residual invasive disease after neoadjuvant chemotherapy, treated consecutively with adjuvant T-DM1 at the various Italian oncology centers.

Inclusion Criteria:

• Histological diagnosis of HER2 positive breast cancer;
• Presence of invasive residual disease on T or N after neoadjuvant chemotherapy including anti-HER2 agents
• Treatment with T-DM1 in the adjuvant post-neoadjuvant setting, in case of positive hormone receptors in combination with adjuvant hormone therapy. Complementary radiotherapy will be allowed as per lines guide;
• Availability of adequate information regarding treatment with adjuvant T-DM1 in accordance with the objectives of the study;
• Written informed consent for the prospective part and, if possible, for the recruited patients retrospectively

Exclusion Criteria:

• Concomitant treatments with other biological agents;
• Absence of clinical data that allow the correct analysis of the primary and secondary objectives;
• Patients with a history of other malignant neoplasms;
• Contraindications to the use of T-DM

HER2 positive breast cancer